1. Field of the Invention
The present invention relates to a semiconductor processing system design. More particularly, the invention relates to a semiconductor processing system and gas panel that provides flexible system configuration, onsite servicing and reduced footprint.
2. Background of the Related Art
Cluster tools for fabrication of semiconductor devices and flat panel displays provide a group of interconnected process chambers and the utilities necessary to operate the chambers. It is not uncommon for a cluster tool to have six or more processing chambers with each chamber having multiple gas supply lines. The total number of gas supply lines can easily exceed twenty. The types of gases typically supplied to these chambers include, but are not limited to, inert gases, reactive deposition gases and reactive etch gases.
For the purpose of controlling and optionally containing the gas supplies, it is desirable to have a common area or enclosure referred to as a gas panel or gas box for isolating control valves, safety shut off valves, actuators, mass flow controllers, associated electronics and the like. The gas box typically sits immediately adjacent to a group of processing chambers, such as adjacent to the chambers attached to a cluster tool, with one side facing the chambers through which each supply line passes. Each gas supply line will have at least one control valve and at least one coupling for connecting a supply line to a chamber. Therefore, the area immediately between the gas box and the processing chambers contains many rigid stainless steel pipes extending in many different directions.
Frequently, even a pipe accurately fabricated according to the construction drawings will run into an obstruction or fail to mate with the appropriate coupling at the chamber or the gas box. The rework required to modify the pipe according to the field dimensions can require as much as two to six hours of skilled labor and adds significantly to the cost of installing this type of equipment.
FIG. 1 is a schematic top view of a cluster tool 10 showing the position and size of a conventional gas panel 12. The individual semiconductor processing chambers 14, which may be any combination of chamber types, are coupled to two transfer chambers 16. Wafer transfer robots 18,20 are positioned within each of the transfer chambers 16 in order pass wafers from one chamber 14 to another chamber 14 or from one transfer chamber 16 to the other transfer chamber 16. Furthermore, the robot 20 is able to reach a load lock chamber 22 where wafers are staged before and after processing in the cluster tool 10. Together, the gas panel 12, transfer chambers 16, processing chambers 14, and the load lock chamber 22 establish the overall footprint of the cluster tool 10.
Many of these chambers require a supply of more than one type of gas in order to perform the intended process on a wafer or a substrate. These gases are typically supplied to the cluster tool through a gas panel or gas box positioned adjacent to the cluster tool. The gas panel is an enclosure which houses a variety of gas controlling components including, but not limited to, flow control valves, flow rate meters, and vials of various volatile liquid precursors, such as dimethyl aluminum hydride (DMAH), that are vaporized for use in the chambers by bubbling a carrier gas through the liquid precursor or through the use of other methods. In this manner, the gas panel functions to isolate the most likely sources of gas leaks from the clean room environment and facilitate collection and disposal of any gas leaking from the components housed therein. Furthermore, the gas panel enables easy access to the gas controlling components for maintenance and installation.
The conventional gas panel 12 houses all of the control valves, shutoff valves, flow meters, volatile liquids and the like that are needed for the operation of the cluster tool 10 and its many chambers 14,16. Gas from the gas panel 12 is typically delivered to the chambers 14,16 from below the chambers 14,16 through stainless steel tubing that is disposed beneath an elevated, false flooring (not shown). Access to the chambers 14,16 for maintenance and installation is maintained by setting the gas panel 12 back a distance 24 from the end of the cluster tool and by installing the tubing beneath the floor.
The process chambers may include, but are not limited to, chemical vapor deposition chambers, physical vapor deposition chambers, etch chambers, cool down chambers and rapid thermal annealing chambers. These chambers variously may require voltage sources, heaters, actuators, vacuum pumps and various sources of reactive or inert gases.
The cluster tool and gas panel are operated inside a clean room in order to prevent or reduce the number of particulate contaminants coming into contact with the semiconductor substrate. However, there is a considerable expense required to operate a clean room and it is desirable to minimize the size of the clean room. It is the cluster tool's footprint (area of floor space) that determines the amount of floor space required in the clean room and the volume of air required to be circulated in order to maintain the contaminant concentration in the air below a given level. Typically, the clean room has a substantial amount of unused space above the cluster tool.
Many different efforts have been directed at reducing the footprint of these processes or devices. Examples of these efforts include redesign of transfer chambers and robots, altering the geometrical configurations of process chambers, relocation of equipment outside the clean room where possible and the like.
Despite these efforts, there is a continuing incentive and need to reduce the footprint of semiconductor processing equipment. It would be desirable to have a cluster tool, complete with process chambers and ancillary equipment, having a smaller footprint without significantly affecting access to the process chambers for maintenance or installation purposes.